1. Field of the Invention
The present invention relates generally to circuit interrupters and, more particularly, to contact assemblies for circuit breakers.
2. Background Information
Circuit interrupters, such as circuit breakers, are employed in diverse capacities in power distribution systems. A circuit breaker may include, for example, a line conductor, a load conductor, a fixed contact and a movable contact, with the movable contact being movable into and out of electrically conductive engagement with the fixed contact. This switches the circuit breaker between an on or closed position and an off or open position, or between the on or closed position and a tripped or tripped off position. The fixed contact is electrically conductively engaged with one of the line and load conductors, and the movable contact is electrically conductively engaged with the other of the line and load conductors. The circuit breaker may also include an operating mechanism having a movable contact arm upon which the movable contact is disposed.
Normally, a movable contact arm is made of solid copper or alloys of copper (e.g., silver bearing copper; a copper alloy with a relatively small percentage of silver), which is a relatively good conductor of both electricity and heat, but which is not as strong as other materials. Hence, it is believed that relatively more copper than is necessary to handle the current (e.g., for thermal conductivity considerations) is typically employed in conventional movable contact arms to handle the current and to provide the needed strength (e.g., rigidity), which adds weight and, thus, increases the moment of inertia.
The structure of the circuit breaker operating mechanism and a contact assembly including the line conductor, fixed contact, movable contact and movable contact arm are designed such that it is desirable to provide current interruption in about a half-cycle, such that the resulting arc is extinguished by the line zero crossing.
There is room for improvement in contact assemblies for circuit breakers.